Appraisal Of Nitrogen Dissolution Characteristic Of Slow-controlled Urea And Effects On Rice Nutrient Utilization And Yield Formation

High amounts of traditional nitrogen fertilizer applied to rice on paddy soil often causes serious ammonia volatilization and nitrate leaching and low recovery of the applied nitrogen. Therefore, increasing public attentions have been paid to the concerns of slow-release fertilizer (sulfur-coated urea SCU), it has developed quickly during the last decade. This study was conducted to determine the N release characteristic of two slow-release urea (SCU) by using special lysimeter microplot in2010and2011on the farm of Yangzhou university. On the side, a field experiment with270kg/ha N fertilizer application was conducted with early maturity late japonica variety nanjing44, in order to learn the effect of two SCU alone or different amount combined with conventional urea (PU) applied as only basal on grain yield and growth characteristics of rice. Relationship between N use efficiency and indexes of rice N accumulation and translocation was analyzed respectively. It is attempted to clear and definite the appropriate pattern of SCU, looking forward to provide theoretical reference for popularization and application of the rice, wheat crops. The main research results are as follow:(1) Slow release fertilizers-Sulfur coated urea (SCU) could significantly reduce the nitrogen content in soil water during early stages after the fertilizers application, and the soil available nitrogen is higher than PU during later grown period. During the rice grown season as a whole, the release dynamics of SCU1goes up and down with an upward tendency at a later stages, but the nutrient release rate maintained a mild lower level. Nitrogen of SCU2was released with greater amount than SCU1during initial stages, and then declined remarkably in later periods. In paddy field, the quantity of nitrogen release factor could significantly affect the amount of ammonium accumulation and distribution in soil water, but nitrate was less affected.(2) With the extension of growth period, N accumulation and uptake rate under different fertilizer treatments, the undergrowth plants can absorb nitrogen increased significantly. N uptake of PU at tillering stage was the highest, in addition to SCU1, other SCU treatments are significantly higher than PU points, with SCU2Potassium processing the highest, followed by SCU2+PU(2:1), SCU2+PU(1:1), SCU1was significantly lower. N uptake rate present obvious stage, N uptake rate of SCU was significantly below the PU points from transplanting to tillering stage. In addition to SCU1potassium, other SCU processing are higher than the PU points from tillering to panicle initiation stage. After panicle initiation stage, Of which only SCU2+PU(1:1) N uptake rate decreased obviously, below the PU. N accumulation and uptake rate of SCU2, SCU1+PU(1:1), SCU1+PU(2:1) and SCU2+PU(2:1) were higher than PU from critical stage of productive tillering to maturing. However, N accumulation and uptake rate of SCU1, SCU2+PU(1:1) were lower, respectively, during the phases from critical stage of productive tillering to elongating and from elongating to heading. It was higher than PU that the amount and the efficiency of N translocation after heading, N production efficiency, N agronomy and recovery efficiency of SCU2, SCU1+PU(1:1), SCU1+PU(2:1) and SCU2+PU(2:1). On the contrary, those of SCU1and SCU2+PU (1:1) were significantly lower than PU, or the differences were not significant.(3) Results showed that compared with the treatments of PU applied alone, the treatments of SCU2, SCU2+PU (2:1), SCU1+PU (1:1) and SCU1+PU (2:1) showed significant increase in the rice yield, dry matter accumulation, stem-sheath usable carbohydrate and spikelets per panicle, and maintained a high level of root a-NA oxidation ability with a small reduction tendency. As for the soil textures, the grain yield and dry matter accumulation in clay soil were slightly higher than those in sandy soil, and the root a-NA oxidation ability during heading and10days after heading were lower in clay soil than in sandy soil, while no apparent difference was found on the a-NA oxidation ability at20or30days after heading. It could be concluded that the application of sulfur-coated urea or its combination with normal urea could both meet the basic needs of rice growth. Combined SCU1and PU had better results than either fertilizer applied solely, the application of SCU2received the best outcome, which was followed by SCU2+PU(2:1), and SCU2+PU (1:1) produced the worst result.